Rotor for gas turbine engine

ABSTRACT

The gas turbine engine rotor can have a body having a solid-of-revolution-shaped portion centered around a rotation axis, the body defining an annular cavity centered around the rotation axis, the annular cavity penetrating into the body from an annular opening, the annular cavity extending between two opposite annular wall portions each leading to a corresponding edge of the opening; and at least one structural plate mounted to and extending between the two opposite annular wall portions and forming an interference fit therewith.

TECHNICAL FIELD

The application relates generally to gas turbine engines and, moreparticularly, to rotors thereof.

BACKGROUND

Rotors of gas turbine engines, which may include or form part of animpeller, fan, compressor, turbine, etc., are often subjected tosignificant centrifugal forces stemming from the relatively highrotational speeds at which gas turbine engines are operated. The rotorsare engineered to withstand these structurally harsh operatingconditions and while static effects are relatively straightforward todeal with, dynamic effects can pose particular engineering challenges.

Minimizing weight is a permanent concern in the aeronautics industry ingeneral, and is a particularly significant concern in the case of rotorssince the weight of rotors can influence the extent of the rotor dynamiceffects which may need to be dealt with by further additional weight atthe shaft. While attempts to limit the amount of material used in therotor, and thus limit its associated weight, have been made, thereremain practical limitations to the designing of the rotor shapehowever, such as limitations imposed by the context of commercial-scaleproduction for instance.

Although known rotors and associated methods are satisfactory to acertain degree, there always remains room for improvement. Particularly,any weight savings which can be achieved is desirable in aero gasturbine applications.

SUMMARY

There is provided a gas turbine engine rotor comprising a body having asolid-of-revolution-shaped portion centered around a rotation axis, thebody defining an annular cavity centered around the rotation axis, theannular cavity penetrating into the body from an annular opening, theannular cavity extending between two opposite annular wall portions eachleading to a corresponding edge of the opening; and at least onestructural plate mounted to and extending between the two oppositeannular wall portions and forming an interference fit therewith.

There is also provided a gas turbine engine comprising a shaft adaptedto rotate about an axis of rotation and a rotor fixed to the shaft, therotor including a body having a solid-of-revolution-shaped portioncentered around a rotation axis and having an annular cavity centeredaround the rotation axis, the annular cavity penetrating into the bodyfrom an annular opening, the annular cavity extending between twoopposite annular wall portions each leading to a corresponding edge ofthe opening; and at least one structural plate mounted to and extendingbetween the two opposite annular wall portions and forming aninterference fit therewith.

There is further provided a method of manufacturing a rotor of a gasturbine engine comprising: providing a rotor body, the rotor body beingsolid and having a solid-of-revolution-shaped portion centered around arotation axis of the rotor; forming an annular cavity in the rotor body,the annular cavity extending between two wall portions of the rotorbody; and mounting at least one structural plate between the two wallportions with an interference fit.

Further details of these and other aspects of the present invention willbe apparent from the detailed description and figures included below.

DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompanying figures, in which:

FIG. 1 is a schematic cross-sectional view of a gas turbine engine;

FIG. 2A is a fragmented longitudinal cross-sectional view of a rotor ofthe gas turbine engine of FIG. 1, with FIG. 2B being an alternateembodiment to the rotor of FIG. 2A;

FIG. 3 is a cross-sectional view taken along lines 3-3 of FIG. 2A;

FIG. 4 is a perspective, axially sectioned, view of a gas turbine enginerotor and shaft assembly;

FIG. 5 is an exploded view of the rotor/shaft assembly of FIG. 4.

DETAILED DESCRIPTION

FIG. 1 illustrates a turbofan gas turbine engine 10 of a type preferablyprovided for use in subsonic flight, generally comprising in serial flowcommunication a fan 12 through which ambient air is propelled, amultistage compressor 14 for pressurizing the air, a combustor 16 inwhich the compressed air is mixed with fuel and ignited for generatingan annular stream of hot combustion gases, and a turbine section 18 forextracting energy from the combustion gases.

Turning now to FIG. 2A, a first example embodiment of a rotor 20 whichcan be adapted to the gas turbine engine 10 is shown. The rotor 20 canbe any one of a plurality of rotary gas turbine engine components suchas an impeller, a fan, a compressor component or a turbine component, toname a few examples.

The rotor 20 has a body 22 which generally has a solid of revolutionshape (except for the rotor blades) centered around a rotation axis 24thereof. In this embodiment, the rotor 20 has an optional axial bore 26to receive a shaft therein. Although only partially shown in FIG. 2A, aplurality of rotor blades 21 extend radially outwardly from the body 22of the rotor 20. The radially-inner (i.e. near the axis 24) portion ofthe rotor 20 can thus be referred to as the hub 28. In this embodiment,the weight of the rotor 20 is addressed (i.e. limited) in part by thepresence of an annular cavity 30 which is generally surrounded by ahollow toroidal-shaped structure of the body 22 of the rotor 20. Thisannular cavity 30 may be enclosed by the body 22 of the rotor 20 on allsides except for the circumferential, radially inwardly opening, gapdefined between axially spaced apart flanges 32 and 34 of the hub 28, aswill be seen.

The annular cavity 30 can be said to penetrate into the body 22 from theaxial bore 26 in the radially-outward direction. The annular cavity 30can be formed as part of the body 22 of the rotor 20 and since it formsa partially open void shape in the body 22, the body 22 can still beformed by casting, forging, machining, by additive materialmanufacturing, and/or by welding two or more body portions together, forinstance.

In the illustrated ‘impeller-type’ embodiment, the wall portions 33, 35forming the axially-opposite walls of the annular cavity 30 correspondto a forward annular flange 32 and a rearward annular flange 34 of therotor 20. A first seat 36 is formed in the radially-inner portion of theforward annular flange 32, and a second seat 38 is formed in theradially-inner portion of the rearward annular flange 34, and theannular opening 31 extends axially between the first seat 36 and thesecond seat 38. One or more structural components, which will bereferred to herein as structural plates 40 for the sake of convenience,is/are interference-fitted between the two seats 36, 38 and used incompression therebetween to impart a force acting to maintain theradially-inner ends of the two annular flanges 32, 34 away from oneanother. This feature is significant as during rotation of the rotor 20at operating speeds, the centrifugal effect can be such that it tends to‘stretch’ the rotor in the radial orientation (i.e. normal to the axis24), thereby bringing the radially inner ends, and seats 36, 38, towardone another. The structural plate(s) 40 acts in compression between theseats 36, 38 against this axially collapsing force in order, at least toa certain extent, to substantially maintain the structural shape of therotor body 22 notwithstanding the forces due to the centrifugal effect.The shaped portions referred to above as ‘seats’ 36, 38, are optional,as in alternate embodiments, the structural plate(s) can be positionedin the annular cavity, directly against the wall portions 33, 35, forinstance. In alternate embodiments, such as a fan embodiment forinstance, the annular cavity can penetrate axially into the rotor bodyand the structural plate(s) can be in the radial orientation, forexample.

This ‘extending’ force exerted by the structural plate(s) 40 onto theseats 36, 38 can be made to increase from the originalinterference-fitted state when the rotor is in operation to ensure thatthe structural plate(s) 40 remain(s) well fixed in place and/or opposethe growing, opposite, ‘compressive’ force stemming from the centrifugaleffect.

In a first example, in an embodiment where the rotor 20 is subjected toa significant increase in temperature during operation, the material ofthe structural plate(s) 40 can be selected with a thermal expansioncoefficient which leads to a greater thermal growth of the plate 40 thanthat of the rotor body 22 itself. For instance, if the rotor body 22 ismade of a single, uniform, material, the structural plates(s) 40 can bemade of a material having a thermal expansion coefficient which isgreater than the thermal expansion coefficient of the uniform materialof the rotor body 22.

In a second example, the structural plate(s) can have a shape whichdynamically reacts to the centrifugal effect by extending substantiallyaxially. For instance, the embodiment shown in FIG. 2B shows astructural plate(s) 140 which has a radially-inwardly-curvedaxial-cross-section shape. In other words, it has a center portion 142which is closer to the axis 124 than the two axial ends, or legs 146,148, which rest in the seats 136, 138. When subjected to centrifugalforce, the central portion 142 is driven radially-outwardly and thecentrifugal force is partially transformed by this shape at the twoaxial ends into an axially directed extension force which pushes theseats 136, 138, and thus the flanges, away from one another, as shown bythe arrows 150. Such a functional shape will be referred to herein as asplayed shape, for convenience. This centrifugal-extending function canfurther be increased or attenuated by increasing or decreasing,respectively, the weight of the central portion 142. To this end, in theembodiment of FIG. 2B, the central portion 142 has a greater thicknessthan the axial ends or legs 146, 148.

The interference-fit of the structural plate(s) 40, 140 into and betweenthe seats 36, 38, 136, 138 can be achieved by any suitable process knownto persons of ordinary skill in this art, such as cold-fitting orpress-fitting for instance. Cold-fitting is particularly suitable inembodiments where the thermal expansion coefficient of the structuralplate(s) 40, 140 is greater than the thermal expansion coefficient ofthe body 22.

An interesting feature of the use of one or more structural plate(s) 40in this manner is the possibility of leaving an aperture extendingacross the general location of the structural plate(s) 40. This canallow the cavity 30 to breathe (heat, water, oil), or even allowboroscopy inspection of the cavity 30 across the barrage of structuralplate(s). The one or more structural plates themselves can be providedwith apertures across their radial thickness, or apertures can beprovided by leaving spacings between the circumferential edges of theone or more structural plates.

Referring to FIG. 3, which shows a transversal cross-section byopposition to the axial or longitudinal cross sections views of FIGS. 1and 2, an embodiment is shown where six independent structural plates 40are used in a circumferentially-interspaced manner, leaving sixcorresponding spacings 50 therebetween. The plates 40 may becircumferentially equally spaced apart, such that the circumferentialspacings 50 are also equally spaced apart. In this example, the spacings50 are specifically sized in a manner to allow inspection of the annularcavity 30 from the axial bore 26 using a given piece of boroscopyequipment, without removing the structural plates 40.

FIGS. 4 and 5 show more exemplary details of a possible embodiment,where the rotor 20 of FIG. 2A is shown mounted to a shaft 19 of the gasturbine engine 10 (FIG. 4), and exploded therefrom (FIG. 5),respectively, for additional clarity and completeness with respect to anembodiment.

The above description is meant to be exemplary only, and one skilled inthe art will recognize that changes may be made to the embodimentsdescribed without departing from the scope of the invention disclosed.For example, the one or more structural plates and the body can beprovided in various shapes or sizes, and can be manufactured usingvarious processes. The longitudinal cross-section of the structuralplate(s) can also be inclined relative to the axis rather than beingrelatively parallel thereto as shown in FIGS. 2A and 2B. In cases wheremore than one circumferentially spaced-apart structural plates are used,the forward annular flange seat and/or the rearward annular flange seatcan include a plurality of circumferentially interspaced seat portionseach being associated to a corresponding one of the structural plates.The rotor can be used as any suitable rotary component of a turbofan gasturbine engine or of any other gas turbine engine type which can have anaxial bore or not. In alternate embodiments, the annular cavity canextend into the body from the rear or the front, in a partially orcompletely axial orientation, rather than extending into the body in theradially-outer direction from a hub, axial bore, or otherradially-inwardly located annular opening; accordingly, in such otherembodiments, the plate or plates can extend fully or partially in theradial orientation, or in any suitable orientation between the axialorientation and the radial orientation. The use of distinctly shapedseats are optional, as in some alternate embodiments, the plate orplates can be positioned directly at a suitable depth in the cavity.Still other modifications which fall within the scope of the presentinvention will be apparent to those skilled in the art, in light of areview of this disclosure, and such modifications are intended to fallwithin the scope of the appended claims.

What is claimed is:
 1. A gas turbine engine rotor comprising a bodyhaving a solid-of-revolution-shaped portion centered around a rotationaxis, the body defining an annular cavity centered around the rotationaxis, the annular cavity penetrating into the body from an annularopening, the annular cavity extending between two opposite annular wallportions each leading to a corresponding edge of the opening; and atleast one structural plate mounted to and extending between the twoopposite annular wall portions and forming an interference fittherewith.
 2. The gas turbine engine rotor of claim 1 further comprisingan aperture in the at least one structural plate providing fluid flowcommunication to and from the cavity across the at least one structuralplate.
 3. The gas turbine engine rotor of claim 1 wherein the at leastone structural plate includes a plurality of structural plates disposedcircumferentially around the rotation axis.
 4. The gas turbine enginerotor of claim 3 wherein the structural plates are circumferentiallyinterspaced from one another by corresponding spacings.
 5. The gasturbine engine rotor of claim 4 wherein at least one of the spacings hasa sufficient dimension to allow boroscopy inspection of the cavitytherethrough from the bore.
 6. The gas turbine engine rotor of claim 1wherein the at least one structural plate has a greater thermalexpansion coefficient than the solid-of-revolution-shaped portion of thegas turbine engine in a manner to increase the compression stress of theinterference-fit to force the frontward annular flange away from therearward annular flange when the body is subjected to a temperaturerise.
 7. The gas turbine engine rotor of claim 1 wherein the bodyincludes a hub disposed at a radially inner end of the body andcircumscribing a bore extending axially through the body, the bore beingadapted to receive a shaft therein, the annular cavity penetratesradially outwardly into the body from the axial bore, and each one ofthe two opposite annular wall portions corresponds to a face of acorresponding one of a frontward annular flange portion of the body anda rearward annular flange portion of the body, each of the forwardannular flange portion and the rearward annular flange portion beinglocated at an opposite axial ends of the annular cavity.
 8. The gasturbine engine rotor of claim 7 wherein the at least one structuralplate has splayed legs reaching the corresponding seats with a centralportion projecting radially inwardly between the splayed legs.
 9. Thegas turbine engine rotor of claim 8 wherein the central portion has agreater thickness than the splayed legs.
 10. A gas turbine enginecomprising a shaft adapted to rotate about an axis of rotation and arotor fixed to the shaft, the rotor including a body having asolid-of-revolution-shaped portion centered around a rotation axis andhaving an annular cavity centered around the rotation axis, the annularcavity penetrating into the body from an annular opening, the annularcavity extending between two opposite annular wall portions each leadingto a corresponding edge of the opening; and at least one structuralplate mounted to and extending between the two opposite annular wallportions and forming an interference fit therewith.
 11. The gas turbineengine of claim 10 wherein the rotor further comprises an aperture inthe at least one structural plate providing fluid flow communication toand from the cavity across the at least one structural plate.
 12. Thegas turbine engine of claim 10 wherein the at least one structural plateincludes a plurality of structural plates disposed circumferentiallyaround the rotation axis.
 13. The gas turbine engine of claim 12 whereinthe structural plates are circumferentially interspaced from one anotherby corresponding spacings.
 14. The gas turbine engine of claim 13wherein at least one of the spacings has a sufficient dimension to allowboroscopy inspection of the cavity therethrough from the bore.
 15. Thegas turbine engine of claim 10 wherein the at least one structural platehas a greater thermal expansion coefficient than thesolid-of-revolution-shaped portion of the gas turbine engine in a mannerto increase the compression stress of the interference-fit to force thefrontward annular flange away from the rearward annular flange when thebody is subjected to a temperature rise.
 16. The gas turbine engine ofclaim 10 wherein the rotor body includes a hub disposed at a radiallyinner end of the body and circumscribing a bore extending axiallythrough the body, the bore adapted to receive a shaft therein, theannular cavity penetrates radially and outwardly into the body from theaxial bore, and each one of the two opposite annular wall portionscorresponds to a face of a corresponding one of a frontward annularflange portion of the body and a rearward annular flange portion of thebody, each of the forward annular flange portion and the rearwardannular flange portion being located at an opposite axial ends of theannular cavity.
 17. The gas turbine engine of claim 16 wherein the atleast one structural plate has splayed legs reaching the correspondingseats with a central portion projecting radially inwardly between thesplayed legs.
 18. A method of manufacturing a rotor of a gas turbineengine comprising: providing a rotor body, the rotor body being solidand having a solid-of-revolution-shaped portion centered around arotation axis of the rotor; forming an annular cavity in the rotor body,the annular cavity extending between two wall portions of the rotorbody; and mounting at least one structural plate between the two wallportions with an interference fit.
 19. The method of claim 18, furthercomprising providing the at least one structural plate with a thermalexpansion coefficient that is greater than that of the rotor body, in amanner to increase compression stress of the interference fit betweenthe structural plate and the forward and rearward ward annular flangeportions, thereby forcing the forward annular flange away from therearward annular flange when the rotor body is subjected to atemperature increase.
 20. The method of claim 18, wherein said formingthe rotor body includes forming an axial bore adapted to receive a shafttherein and extending axially through the body concentric with the axisof rotation, and a radially inner end of the body defining a hub whichcircumscribing the bore; said forming the annular cavity is done in amanner that the annular cavity penetrate radially outwardly into therotor body from the axial bore to form a forward annular flange portionof the hub and a rearward ward annular flange portion of the hub, theforward annular flange portion and the rearward ward annular flangeportion being axially spaced apart and located at opposite axial ends ofthe annular cavity and each having a corresponding seat in the hub;further comprising forming the at least one structural plate in a mannerthat splayed legs reach the corresponding flange portions and a centralportion of the structure plate projecting radially inwardly between thesplayed legs thereof; and wherein said mounting the structural plate isdone in a manner that the structural plate extend at least partiallyaxially between the forward and rearward ward annular flange portions.